Ultrasonic welding uses high frequency ultrasonic acoustic vibrations to hold materials together. Such systems contain an ultrasonic horn assembly having a number of distinct components, which are connected in a stack. Common configurations include a converter to convert electrical signal into a mechanical vibration, a booster to modify the amplitude of the vibration, and a horn to apply mechanical vibrations to the parts to be welded. In standard systems the booster is also used to clamp the stack into a press.
The most typical mounting method for an ultrasonic stack is supporting the horn, preferably at its nodal point, in order to prevent loading of the tip by the anvil from deflecting the horn off the transducer axis. Several nodal mounting means have been devised such as set screws, clamps, and spring mounting. With such mounting systems, the horn deflects when weld force is applied causing the interface between the horn and anvil to hinge open. This results in loss of energy transmission and a loss of positional accuracy. Additionally, the horn has no radial orientation feature because it is screwed onto the booster. A skilled technician with special set up tools is therefore required to accurately orient the horn.
Another disadvantage of the prior art lies in the lack of accuracy and rigidity of the weld position. In many applications such as wire splicing and wire termination, the position of the weld tip must be maintained within 3 microns (0.001 inches). This is not possible to achieve under full load of prior mounting systems. For example, U.S. Pat. No. 4,610,750 to Branson Ultrasonics Corp. shows a replaceable tip mounted onto the tapered end of a round horn. A problem with this design is limited access to weld larger components due to interferences with the body of the horn.
What is desired, therefore, is an ultrasonic welder where the body is nodally and radially mounted, and also is self-aligning with respect to the housing. A self-positioning horn with a replaceable, self-aligning weld tip is also desired.